Human body like an engine needs fuel for energy which it has to generate in the course of its physiological functions. The work done by human body like any other living organism is mechanical and biochemical . The fuel for the production of this energy is food. Food has to be digested , absorbed and broken down into simple substances which are utilized to build body tissues as well as to produce energy.
Man is the highest evolved animal in nature. So far as animals are concerned, they know their food by instinct. They also know , to a considerable extent, what to eat. The quantity of food taken by them is governed by their appetite which in turn is regulated by the energy needs as well as by storage requirements. Tastes do play some part in the food intake by higher animals but primarily it is the appetite and instinctive selection of food. Therefore, qualitatively and quantitatively the food intake depends on the physiological requirements. This is fairly true of animals in their natural habitat uninterfered by human influences. Of course , it depends upon the availability of food. Also, animals do not stick to regular food timings and there are no significant compulsions in eating as found in man.
The primitive man ate mostly according to his instinctive requirements. Gradually , however , with development of working , discoveries of varieties of food and the evolution of society , many extraneous factors started playing significant role in human dietary habits. Our ancestors had to exert a lot in their daily life. With the advent and advancement of civilization , the expenditure of energy became less and less and food habits started developing with more dependence on taste and social eating . The economic environment played a strong role in the qualitative and quantitative parameters of food intake.
The main items of food , technically speaking can be said to be proteins, fats, carbohydrates , vitamins & minerals. Out of these , proteins act as tissue builders of the body; fat act both as fuel as well as energy storage depots. They also act as carriers of certain important fat soluble vitamins . The cabohydratesare mainly responsible for production of energy. All these types of food can be utilized by the body to produce energy. The body proteins are the last to be utilized in the process of drawing on the tissue resources. A deficiency in proteins in diet , leads to muscle wasting as well as breakdown of body resistance to infection and other diseases including hormones deficiencies and anaemia. Minerals in small quantities are also essential in the electrical processes taking place on the outside and inside the cellular structure.
However , with the development of economy , industrialization and consequent affluence in many developed and developing countries, the circumstances have changed. Formerly, many lives used be lost due to insufficient food intake. Now, in many affluent countries, more people are dying due to over eating than by under nourishment.
How does this all happen ? For the answer to this question we have to look at the pattern of modern affluent life. Sedentary habits of people have increased with the increase of sedentary occupations. Modern transport facilities have obviated the need for the long distance walking or even short distance walking. People will wait for a bus or a lift for considerable time rather than walk a few blocks or climb a storey or two. With the advent of machine age , manual work has been reduced. Eating habits have changed and with them have been evolved rich food dishes , which cater to the palate than to the needs of the body. The manual worker used to require much food as compared to the intellectual sedentary worker.
Eating rich food has become a status symbol and gradually the appetite of affluent people gets adjusted to intake of larger quantities of food. Even this in itself is undesirable but to go a step further , the qualitatively proportion of food ingredients also gets disturbed.
Let us deal with the over intake of food. This results in gain of weight and obesity. Apart from inconvenience in day to day functioning of an individual , lethargy and loss of useful man hours to the society , the life span of an over weight person is shorter. This has been amply proved by statistical assessment of large population groups. Disease like hypertension , diabetes , arthritis , gout and digestive disturbance go hand in hand with excessive weight. Injuries like fractures , operations and even healing of ordinary wounds are also hazardous in obese (fatty) persons